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Scale Rules

Rules for Drafting

To create technical drawings such as those presented by the traveling exhibition, Doodles, Drafts, and Designs, draftsmen needed drawing instruments with specialized scales. Most often, their goal was to represent a real-life place or object at a reduced proportion. Thus, drafting rules like those shown on this page were typically marked for making drawings at scales such as 1/8-inch to 1 foot. Sometimes, instead of marking the increments throughout a scale, only the first and last segments of a scale were subdivided to the desired proportion. These were called open divided or architect's scales.

Rules for drafting sometimes had plotting scales. These were divided into equal increments of a useful length, such as 1/2-inch, that could be directly transferred to a drawing such as a surveying map. At both ends, plotting scales typically had diagonal scales. These allowed users to reasonably accurately estimate the decimal division between two markings on a scale. Instruments in this category also may have a line of chords. This projected the distance between the end of a quarter-circle arc and each of the degrees along the arc onto a straight line. Finally, the scales for measuring lengths on rules for drafting were often divided into multiples of 1/10-inch, called chain scales, which were advantageous for activities such as construction or machine work.

This two-sided boxwood rule has a scale of chords and architect's scales dividing the inch into 40, 35, 30, 25, 20, and 15 parts on one side. A white sticker on that side is marked: 783. The other side has an inch scale divided to 1/10" and numbered by ones from 1 to 6; a scale divided to ones and numbered by tens from 10 to 50 (10 units is approximately 3 cm); and 5" plotting scales with diagonal scales at each end. One plotting scale is divided to 1/2" and numbered by ones from 10 to 1, and the other is divided to 1/4" and numbered by ones from 1 to 18. One edge of the rule is scalloped.

The previous owner collected more than 1,200 hand tools and machine tools and displayed them at his family's building company in Baltimore, Md. This object was item number 783 in his collection. It probably dates to the turn of the 20th century. Similar scales were sold for 10¢ to 15¢ by Dietzgen (model number 1690) from at least 1902 to 1912 and by Keuffel & Esser (model number 1616) from at least 1892 to 1913. Both companies stopped advertising the object before 1921.

Frank G. Hunt of Buffalo, N.Y., designed this flexible steel rule for drawing straight lines on curved surfaces, such as those of ledger books. The rule has no scales, but it has a small round metal handle in the middle of the front. Nine rectangular clips on the back hold several layers of paper covered by a metal rectangle. The middle clip is marked: EXP. ACC'T. F. G. HUNT (/) PAT'D. FEB.25.02 (/) BUFFALO, N.Y. Hunt distributed the rule via the Hunt Ruler Company in Buffalo at least as late as 1920. By 1922, he had passed away but the firm was expanding.

This undivided, black hard rubber rule is beveled along both long edges. It is marked: EBERHARD FABER (/) NEW YORK. John Eberhard Faber (1822–1879) began making pencils in New York City in 1861. In 1872 his factory moved from Manhattan to Brooklyn, where it remained until 1956. The company also made and sold other office supplies, expanding in 1898 by forming the Eberhard Faber Rubber Company of Newark, N.J., to make erasers and rubber bands. Compare this object to MA*319738.

This undivided black hard-rubber rule is beveled along both long edges. It is marked: I. R. C. CO. (/) GOODYEAR. Scratched on the back of the rule is: Brereton. IRC, or Inoue Rubber Company, was established in Japan in 1926 to make bicycle tires and tubes. The reference to Goodyear is likely to the manufacturing process pioneered by Charles Goodyear and not to the Goodyear Tire & Rubber Company. Brereton was presumably the original owner of the instrument, which was acquired by the Museum in 1961. Compare to MA*327306.